1. Technical Field
The present invention generally relates to a single-inductor dual-output (SIDO) power converter operable in a discontinuous conduction mode (DCM) and, more particularly, to a SIDO power converter and a control method thereof, capable of dynamically adjusting the phases of clock signals with respect to the loads according to a load difference therebetween to achieve optimal power distribution.
2. Description of Related Art
With the development of technology, single electronic devices have evolved to provide multiple functions. Therefore, it is crucial to provide a power converter capable of supplying multiple voltage levels to meet the requirements of the multiple functions of the electronic device. A single-inductor dual-output (SIDO) power converter, in which only one inductor element is used to provide two output voltage levels, is a proper candidate with minimal size, low cost and high conversion efficiency.
Referring to FIG. 1, FIG. 1 is a circuit diagram of a conventional SIDO power converter. More particularly, the SIDO power converter 1 includes an inductor L, a first switch SW1, a second switch SW2, diodes 10, 12, capacitors 14, 16, and a pulse width modulation (PWM) control circuit 18. The PWM control circuit 18 controls the first switch SW1 and the second switch SW2, respectively, to be turned on or off so that the SIDO power converter 1 is capable of providing two different output voltage levels VSP, VSN. The SIDO power converter 1 further operates in a discontinuous conduction mode to prevent cross regulation. Therefore, the SIDO power converter 1 is configured to switch between a boost mode and a buck-boost mode. In other words, the SIDO power converter 1 operates alternately in the boost mode and the buck-boost mode. Once the inductor L finishes storing and releasing energy in the boost mode, the inductor L is switched to operate in the buck-boost mode to recharge the output capacitor.
Referring to FIG. 2, FIG. 2 illustrates the waveform when the SIDO power converter FIG. 1 operates. The waveform 20 indicates the change of the inductor current IL, where T1 is the cycle of the boost mode, T2 is the cycle of the buck-boost mode, and each of the cycle T1 and the cycle T2 includes an idle period T1IDL and T2IDL, respectively, when the inductor current IL is zero. Accordingly, since the switching between the boost mode and the buck-boost mode remains at a constant frequency (i.e., T1=T2), the buck-boost mode with the longer idle period T2IDL exhibits lower power conversion efficiency and larger power loss.